Hawaiian Wave Patterns— -Emery 
257 
Fig. 1. Weather map for 1600 Honolulu time (0600 G.C.T.) on 31 August 1961. The winds and isobars 
are typical of the season for the Hawaiian Islands, except for the minor low to the southeast. Courtesy of 
Charles Roberts of Honolulu office of U. S. Weather Bureau. 
of another kind, ones which are commonly sev- 
eral km long, 20-200 m wide, broadly sinuous, 
and 1 or more km apart. Their general trend 
happened to be more or less perpendicular to 
the wind and parallel to shore. These slicks are 
typical of convergences above shallow internal 
waves (Ewing, 1950; LaFond, 1959). A third 
kind of slick was noted behind a ship — straight, 
parallel-sided, about 30 m wide, and oily brown. 
It clearly resulted from ship wastes, probably 
from pumping of bilges or fuel tanks. 
WAVES 
Instead of the anticipated single train of 
waves, the area was found to contain three trains 
of large long-period waves and several trains 
of small short-period ones. Many measurements 
of the former waves revealed an average of 
7 -sec period, whereas the latter were 1 sec or 
shorter. Most of the wave energy was confined 
to the two trains of 7-sec waves coming from 
the east (090°) and southeast (130°). The 
train from the east was slightly sharper crested, 
perpendicular to the wind slicks ( compare Figs. 
2 and 3 ) , and most frequently topped by white- 
caps. Interference between these two trains 
caused the sea surface to be broken into a 
diamond-shaped pattern, each block of which 
contained a short section of wave crest. 
Along the sides of the islands, wave refraction 
caused the waves to bend and to approach paral- 
lelism with shore, but the width of the zone 
was generally too small to map on the scale of 
the survey. At the straits the waves took a circu- 
lar front, evidently due to diffraction (Arthur, 
1951). The shapes of the wave fronts are similar 
to those of the tsunamis studied by Shepard, 
Macdonald, and Cox (1950) in the Hawaiian 
region, but the latter are controlled more by 
refraction than by diffraction owing to their 
great wave length. Spreading of the circular 
